Metallo-dielectric Electromagnetic Bandgap Research Articles

A Dual-Perforation Electromagnetic Bandgap Structure for Parallel-Plate Noise Suppression in Thin and Low-Cost Printed Circuit Boards

In this study, we propose and analyze a dual-perforation (DP) technique to improve an electromagnetic bandgap (EBG) structure in thin and low-cost printed circuit boards (PCBs). The proposed DP–EBG structure includes a power plane with a square aperture and a patch with an L-shape slot that overcomes efficiently the problems resulting from the low-inductance and the characteristic impedance of the EBG structure developed for parallel-plate noise suppression in thin PCBs. The effects of the proposed dual-perforation technique on the stopband characteristics and unit cell size are analyzed using an analytical dispersion method and full-wave simulations. The closed-form expressions for the main design parameters of the proposed DP–EBG structure are extracted as a design guide. It is verified based on full-wave simulations and measurements that the DP technique is a cost-effective method that can be used to achieve a size reduction and a stopband extension of the EBG structure in thin PCBs. For the same unit cell size and low cut-off frequency, the DP–EBG structure increases the stopband bandwidth by up to 473% compared to an inductance-enhanced EBG structure. In addition, the unit cell size is substantially reduced by up to 94.2% compared to the metallo–dielectric EBG structure. The proposed DP–EBG technique achieves the wideband suppression of parallel plate noise and miniaturization of the EBG structure in thin and low-cost PCBs.

Effect of forbidden bands of electromagnetic bandgap engineered ground plane on the response of half wave length linear microwave resonator

This paper reports a detailed experimental analysis on the effect of forbidden bandgaps of planar metallo-dielectric electromagnetic bandgap (EBG) structures as ground plane of a half wavelength linear resonator. It is observed that the resonator with metallic square and triangular lattice as ground plane results in resonance shifting to higher values whereas, on patterning negative structures of the said lattice which we mention as dielectric lattice in this paper, did not result in any appreciable change. Simulation and experimental results illustrate appreciable increase in quality factor and decrease in insertion loss for metallic EBG on the ground plane, while marginal reduction in insertion losses and increase in quality factor has been obtained with dielectric lattice.

Miniaturisation schemes for metallodielectric electromagnetic bandgap structures

Two miniaturisation schemes for metallodielectric electromagnetic bandgap (MEBG) arrays are presented. Miniaturisation by virtue of the closely coupling technique as well as by employing complex element geometries is demonstrated by means of full-wave simulations and experimental results. A combination of the two techniques is shown to produce a further miniaturisation. An MEBG array with unit cell λ/35 is experimentally demonstrated. The concepts are expanded for the miniaturisation of artificial magnetic conductor (AMC) surfaces. It is demonstrated that there is a trade-off between AMC miniaturisation and bandwidth. The motivation behind the miniaturisation is demonstrated with a test mobile handset employing a miniaturised conformal MEBG surface. The handset's antenna efficiency and frequency detuning are improved in the presence of the user's hand.

2-D characterisation of electromagnetic bandgap structures employed in power distribution networks

A two-dimensional (2-D) analytical approach, based on the transmission-line modelling of metallo-dielectric electromagnetic bandgap (EBG) structures, is presented. This analysis technique is exploited to investigate the band diagrams of the EBG structures embedded in a parallel-plate power distribution network; an arrangement which is commonly used for global suppression of switching noise in high-speed circuits. Complex 2-D Bloch analysis is utilised in the proposed methodology to obtain the 2-D attenuation diagrams corresponding to the 2-D dispersion curves, in a matter of few seconds. The insertion loss information extracted from these attenuation diagrams is employed in predicting the efficiency of the noise suppression method.

High-gain subwavelength resonant cavity antennas based on metamaterial ground planes

Planar metamaterial surfaces with negative reflection phase values are proposed as ground planes in a high-gain resonant cavity antenna configuration. The antenna is formed by the metamaterial ground plane (MGP) and a superimposed metallodielectric electromagnetic band gap (MEBG) array that acts as a partially reflective surface (PRS). A single dipole positioned between the PRS and the ground is utilised as the excitation. Ray analysis is employed to describe the functioning of the antennas and to qualitatively predict the effect of the MGP on the antenna performance. By employing MGPs with negative reflection phase values, the planar antenna profile is reduced to subwavelength values (less than λ/6) whilst maintaining high directivity. Full-wave simulations have been carried out with commercially available software (Microstripes™). The effect of the finite PRS size on the antenna radiation performance (directivity and sidelobe level) is studied. A prototype has been fabricated and tested experimentally in order to validate the predictions.

Comparative Investigation of Coupling Reduction by EBG Surfaces for Quasi-Static RCS Measurement Systems

It is proposed to reduce the E-plane coupling of two horn antennas, a configuration often used for quasi-static radar cross section (RCS) measurements, by means of a printed metallo-dielectric electromagnetic bandgap (EBG) surface of the mushroom type. It is shown by experiments that the performance of the printed EBG surface is superior to that of standard absorbing materials and a corrugated surface of the soft type. The printed EBG surface and the corrugated surface are designed by finite-element method (FEM)-based eigenmode analysis.

Miniaturization of electromagnetic band gap structures for mobile applications

It is well known that interference of the human body affects the performance of the antennas in mobile phone handsets. In this contribution, we investigate the use of miniaturized metallodielectric electromagnetic band gap (MEBG) structures embedded in the case of a mobile handset as a means of decoupling the antenna from the user's hand. The closely coupled MEBG concept is employed to achieve miniaturization of the order of 15:1. Full wave dispersion relations for planar closely coupled MEBG arrays are presented and are validated experimentally. The performance of a prototype handset with an embedded conformal MEBG is assessed experimentally and is compared to a similar prototype without the MEBG. Reduction in the detuning of the antenna because of the human hand by virtue of the MEBG is demonstrated. Moreover, the efficiency of the handset when loaded with a human hand model is shown to improve when the MEBG is in place. The improvements are attributed to the decoupling of the antenna from the user's hand, which is achieved by means of suppressing the fields in the locality of the hand.

A simple and effective model for electromagnetic bandgap structures embedded in printed circuit boards

Using a transmission-line model and considering a simple lumped-element substitute for the patch-via structure, a first-order, but detailed, quantitative and qualitative analysis of the filtering properties of a metallo-dielectric electromagnetic bandgap structure embedded in a printed circuit board is presented. This model is able to describe the resonant properties of the structure as well as its pass-band and stop-band regions.

An electromagnetic bandgap curl antenna for phased array applications

A promising way to reduce the problems created by surface waves in printed phased array antennas is to use an electromagnetic bandgap (EBG) substrate instead of a standard dielectric. Two metallo-dielectric EBG substrates well suited for phased array applications have been designed and tested. One of them has a compact unit cell and exhibits a broad bandwidth performance. The other EBG structure has a narrower bandwidth but is simple to manufacture and has a low mechanical profile. Single radiating elements and a small linear array have been manufactured on a standard dielectric substrate and on the EBG substrates. The measurements show a significant improvement in radiation efficiency as well as of the front to back ratio for the antennas manufactured on the EBG substrates compared to the ones obtained for the antennas manufactured on the standard dielectric substrate. These results clearly demonstrate the effectiveness of the EBG substrates in reducing the surface and guided waves.

Electromagnetic Interference (EMI) Reduction From Printed Circuit Boards (PCB) Using Electromagnetic Bandgap Structures

As digital circuits become faster and more powerful, direct radiation from the power bus of their printed circuit boards (PCB) becomes a major concern for electromagnetic compatibility engineers. In such multilayer PCBs, the power and ground planes act as radiating microstrip patch antennas, where radiation is caused by fringing electric fields at board edges. In this paper, we introduce an effective method for suppressing PCB radiation from their power bus over an ultrawide range of frequencies by using metallo-dielectric electromagnetic band-gap structures. More specifically, this study focuses on the suppression of radiation from parallel-plate bus structures in high-speed PCBs caused by switching noise, such as simultaneous switching noise, also known as Delta-I noise or ground bounce. This noise consists of unwanted voltage fluctuations on the power bus of a PCB due to resonance of the parallel-plate waveguiding system created by the power bus planes. The techniques introduced here are not limited to the suppression of switching noise and can be extended to any wave propagation between the plates of the power bus. Laboratory PCB prototypes were fabricated and tested revealing appreciable suppression of radiated noise over specific frequency bands of interest, thus, testifying to the effectiveness of this concept.

Closely Coupled Metallodielectric Electromagnetic Band-Gap Structures Formed by Double-Layer Dipole and Tripole Arrays

The concept of closely coupled metallodielectric electromagnetic band-gap (CCMEBG) structures is introduced and investigated using two-dimensional (2-D) double-layer dipole and tripole arrays. An efficient numerical method based on a set of coupled integral equations is used to simulate the double-layer array response. The arrays are placed in close proximity to each other and shifted appropriately in order to produce maximum element coupling. Measurements are presented for oblique plane wave and surface wave incidences. A substantial decrease of the stopband center frequency is observed with the CCMEBG design for both element geometries. Furthermore, wider bandwidth and improved angular stability as compared to single-layer MEBG is obtained. The tripole arrays arranged on a hexagonal lattice exhibit common stopband for any polarization of the incident field due to the symmetry of the element in conjunction with the lattice. The lowering of the resonance for up to 4 to 1 in simulation results emerges as the layers are separated by less than /spl lambda//1200 (0.1 mm at 2.5 GHz).

Periodically loaded 1-D metallodielectric electromagnetic bandgap structures for miniaturisation and bandwidth enhancement

Periodic loading of 1-D metallodielectric electromagnetic bandgap (MEBG) structures has been rigorously investigated. Miniaturised and broadband MEBG structures have been produced by means of periodically loading a dipole array. A study has been carried out with regard to the loading mechanism, the number of stubs, the topology of the structure and the order of loading. Simulations have been carried out using a method of moments based software. First order uniform loading stubs have yielded a significant size reduction of the MEBG array and the bandwidth has doubled. Good agreement between simulations and measurements has been achieved. The current distribution on the proposed structure has been studied, yielding valuable insight. An interdigital topology has resulted in further miniaturisation and bandwidth enhancement. Fractal-type arrays have been produced after applying second order loading. A maximum miniaturisation of 2.5:1 has been achieved.

Metallo-dielectric electromagnetic bandgap structures for suppression and isolation of the parallel-plate noise in high-speed circuits

A novel approach for the suppression of the parallel-plate waveguide (PPW) noise in high-speed printed circuit boards is presented. In this approach, one of the two conductors forming the PPW is replaced by an electromagnetic bandgap (EBG) surface. The main advantage of the proposed approach over the commonly practiced methods is the omnidirectional noise suppression it provides. For this purpose, two EBG structures are initially designed by utilizing an approximate circuit model. Subsequently, the corresponding band structures are characterized by analytical solutions using the transverse resonance method, as well as full-wave finite-element simulations. The designed EBG surfaces were fabricated and employed in a number of PPW test boards. The corresponding frequency-domain measurements exhibited bandgaps of approximately 2.21 and 3.35 GHz in the frequency range below 6 GHz. More importantly, suppression of the PPW noise by 53% was achieved based on time-domain reflectometry experiments, while maintaining the signal transmission quality within the required specifications for common signaling standards.

FDTD Simulations of Reconfigurable Electromagnetic Band Gap Structures for Millimeter Wave Applications

Metallo-dielectric electromagnetic bandgap (EBG) structures are studied in the millimeter regime with a finite difference time domain (FDTD) simulator. Several EBG waveguiding structures are considered for millimeter-wave power splitting, switching and filtering operations. It is demonstrated that triangular EBG structures lend themselves naturally to the design of Y-power splitters. Square EBG structures with circular and square rods are shown to lead naturally to straight in-line waveguide filter applications. Comparisons between EBG millimeter-wave waveguide filters formed with dielectric and metallic rods are given. It is shown that high quality broad bandwidth, millimeter-wave bandstop filters can be realized with square EBG structures with circular metallic rods. It is demonstrated that multiple bandstop performance in a single device can be obtained by cascading together multiple EBG millimeter-wave waveguide filters. It is also demonstrated that one can control the electromagnetic power flow in these millimeter-wave EBG waveguide devices by introducing additional local defects. It is shown that the Y-power splitter can be made reconfigurable by using imposed current distributions to achieve these local defects and, consequently, that a millimeter-wave EBG switch can be realized.